The skeleton is the support system of land animals and its joints are key to its structural integrity in everyday life. Examining this integrity for the purpose of understanding malfunction in the living organism, without penetrating the surface, has hitherto been an insurmountable problem, preventing accurate diagnosis and informed treatment. This has meant that the functional integrity of joints, especially the spinal joints, could not be assessed in living subjects without resorting to invasive procedures. Spinal fusions, often a last resort for intractable back pain, could not be inspected for their success without revision surgery, and suspected disruption of ligaments could not be objectively assessed.
Attempts to overcome this difficulty by placing measuring devices on the surface of body segments, and recording their displacements during movement of the body were unsatisfactory because it was surface (skin) rather than bone motion that was recorded—especially in relation to the segments of the spine. The use of plain X-rays was also unsatisfactory because only the beginning and end of the motion could be recorded without giving a prohibitive radiation dose. Attempts involving cineradiography and videofluoroscopy allowed the whole range of motion to be seen on film or videotape, but not measured. Furthermore, marking a sufficient number of the images in a motion sequence manually, in pursuit of such measurement, was too laborious to support a method for use in clinical settings. See, for example, U.S. Pat. No. 5,090,042. Additionally, voluntary motion of joints adds the confounding factor of the stabilising influence of the muscles, concealing any abnormality of the joint ligaments or other passive elements, notably the intervertebral discs.
There is, therefore, a need for a system that provides a means for producing real-time image generation of the motion of the bones in a subject than can objectively measure the functional integrity of joint tissues with the minimum of invasiveness.